Rainstorm regulates phosphorus composition and migration along an ecological continuum of mudflat-mangrove-creek.

Phosphorus is a critical factor that influences the eutrophication of nearshore seawater. With global climate change, how the increasing frequency of rainstorm events alter the phosphorus characteristics of coastal sediments remain unclear. This study found that rainstorm caused the accumulation of phosphorus in the tidal flat, and the concentration of total phosphorus (TP) increased from 505.18(344.92-1066.80) mg/kg to 759.04(378.18-2077.50) mg/kg. The exogenous input and endogenous transformation of phosphorus forms jointly let the increase in phosphorus content. The response process of each habitat to rainstorm is different. The enrichment of organic phosphorus increased the bioavailable phosphorus (BAP) content, leading to an increased risk of phosphorus pollution (BAP/TP in mudflats, from 38.83% to 46.08%; BAP/TP in tidal creeks, from 44.24% to 47.56%). However, in mangroves, biological disturbance alleviates pollution risks (BAP/TP from 44.92% to 40.36%). These findings enhanced understanding of the response of biogenic elements in coastal wetlands to extreme rainstorm events.